Research & Development On Novel Shape-Memory Polymers

In this paper polyethylene(PE), ethylene-vinyl acetate copolymers(EVA) and poly(ε-caprolactone) - ethylene-vinyl acetate copolymers blends(PCL/EVA) were crosslinked by dicumyl peroxide(DCP) or γ-ray, and shape-memory polymers were prepared. Some macroscopic and microscopic factors, which influence the shape-memory properties, processability and mechanism, were studied by mensuration of memory properties & gel content, optical microscope, Differential Scanning Calorimeter and Dynamical Mechanical Thermal Analysis.It is found that the shape-memory behavior and mechanism has great relationship with the content of DCP, the irradiation dose, the content of gel, the strain ratio, crystallinity and the average molecular weight between the cross-linkage point (Mc). The recovery temperature is corresponding to the melting point of the polymer that isn't crosslinked; the recovery temperature is 5～10℃ below the melting temperature of the polymer and is influenced by crystallinity. The shape recovery rate, recovery speed and recovery stress are mainly affected by the content of DCP, the irradiation dose, the content of gel and Mc. The influence of crystallinity,the content of DCP and the irradiation dose on shape fixity rate is prominent. The crystallinity has great influence on the service performance. The strain ratio has little influence on the shape memory properties. The average molecular weight between the cross-linkage point is a determining factor influencing the shape memory properties and can accurately character the shape memory properties relative to gel content. The shape memory polymers with excellent properties can be prepared by controlling the content of DCP or the dose of irradiation.